Scissors

From Academic Kids

(Redirected from Scissor)
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Scissors.jpg
Different types of scissors - sewing, kitchen, paper

Scissors are a tool used for cutting thin material which requires little force. They're used for cutting, for example, paper, cardboard, metal foil, thin plastic, food, cloth, rope and wire. They are also used for cutting hair and nails.

Unlike a knife, scissors have two hinged blades. Most types of scissors are not particularly sharp; it is primarily the shearing between the two blades which cuts. Children's scissors are even less sharp, and are often protected with plastic.

Although commonly ascribed to Leonardo da Vinci, scissors were likely invented in 1500 BC in ancient Egypt[1] (http://inventors.about.com/library/inventors/blscissors.htm). These were likely shears with the joint at the far end[2] (http://www.everything2.com/index.pl?node=scissors). Modern cross-bladed scissors were invented by Romans around AD 100.

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Schere_Gr_99.jpg


Mechanically, scissors are a first-class, double-lever with the pivot/hinge acting as the fulcrum. For cutting thick or heavy material, the mechanical advantage of a lever can be exploited by placing the material to be cut as close to the fulcrum as possible. For example, if the applied force (i.e. the hand) is twice as far away from the fulcrum as the cutting location (e.g. piece of paper), the force at the cutting location is twice that of the applied force at the handles. Specialized scissors, like bolt cutters exploit leverage by having a long handle but placing the material to be cut close to the fulcrum.

Left handed scissors

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2scissors.jpg
left-handed (left) and right-handed (right) scissors

Consider the case of a paper cutter. It clearly is left-handed or right-handed. Scissors are mechanically equivalent to paper cutters and likewise can be left or right-handed.

Because scissors have overlapping blades, scissors are not symmetric. This asymmetry is true regardless of the orientation and the shape of the handles: the blade that is on top always forms the same diagonal regardless of orientation. Human hands are also asymmetric and worse, when closing the thumb and fingers do not close vertically, but have a lateral component to the motion. Specifically, the thumb pushes out and fingers pull inwards. For right-handed scissors, the thumb blade is closer to the body so that the natural tendency of the hand forces the cutting blades together. Furthermore, with right-handed scissors held by the right-hand, the shearing edge is visible. Conversely, if a right-handed scissor is held in the left hand, the natural tendency of the left hand would be to force the cutting blades laterally apart. Worse, the cutting edge of the scissors would be behind the top blade, and one cannot see what is being cut.

Ambidextrous scissors are not truly ambidextrous. They have symmetric handles so their is no distinction between the thumb and finger handles. They have very strong pivots so that the blades simply rotate and do lot have any lateral give. However, even if the scissor successful cuts, the blade orientation will block the view of the cutting line of the left-handed person.

Using scissors designed for the wrong hand is very difficult for most people. They have to unnaturally force the blades together to cut and stretch their necks over the top blade to see what is being cut.

Specialized scissors

Other meanings

Scissors is also a party game as is Rock, Paper, Scissors.

Scissoring is also a lesbian sex term. Where spread out their legs in opposite directions and interlock with the other person while rubbing back and forth.de:Schere ko:가위 nl:Schaar ja:鋏 pl:Nożyczki ru:Ножницы simple:Scissors sl:Škarje fi:Sakset sv:Sax

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